the basic idea to implement event capturing in IE is fairly simple. First you have to realize that event capturing is only needed for “bubbling” events. These events always bubble up to the document body.

We have our own implementation of “addEventListener” which does not attach a native event listener to the given DOM element but instead uses a common event listener for this event on the document body. This common generic event listener receives all events of a type and by inspecting the event’s original event target it is able to build the chain of DOM nodes up to the body. With this information together with the knowledge of all event listeners we can do the dispatch ourselves. We simply walk from the body to the target and call all capturing event handler and then walk back from the target to the body to call the bubbling event listeners.

There is always only one native event listener for each bubbling event of a type, which is attached to the body.